It is well known that metal can be extracted from metal ions in an electrolytic solution through an electrowinning process. An electrowinning process utilizes the known technique of plating metal or metal compounds out of an electrolytic solution onto an electrode plate. Modern electrowinning typically occurs in a relatively large, non-conductive tank that contains metal ions dissolved in an electrolytic solution. A plurality of side-by-side, parallel cathode and anode plates are suspended in the electrolytic solution. In a copper electrowinning cell, the cathodes and the anodes are ultimately arranged such that each cathode is disposed between two anodes. The cathodes and anodes are connected to an electrical power source to cause the plating of copper onto the cathode plates.
Electrowinning cells typically include a circulating system that circulates the electrolytic solution from a reservoir to the electrowinning cell and back to the reservoir. Metal ions depleted from the electrolytic solution during the electrodeposition process, are replenished in the reservoir. The replenished (i.e., “fresh”) electrolytic solution is pumped into the electrowinning tank, typically at the bottom thereof. Excess solution in the tank overflows the upper edge of the tank and is collected in a trough. The collected (i.e., “metal depleted”) electrolyte is returned to the reservoir.
This type of arrangement produces a less than desirable flow of the electrolytic solution in the tank. The electrolytic solution typically flows from its point of entry at the bottom of the tank toward the edge of the tank where the solution exits, i.e., overflows, the tank. This produces areas of lower flow between the plates, that is more marked in the middle of the upper region of the tank. The flow of the electrolytic solution is also influenced by gas bubbles that form between the electrode plates during the electrodeposition process, as gas is liberated at the surface of the anode plates. These gas bubbles also tend to direct the electrolytic solution away from the spaces or gaps between the parallel anode and cathode plates toward the sides and edges of the tank. Thus, the replenished, fresh electrolytic solution forced into the tank typically flows toward the edges of the tank where it overflows the tank, rather than into the cathode and anode gaps where the actual electrodeposition occurs and where the replenished electrolytic solution is needed.
The present invention overcomes these and other problems and provides an electrowinning cell and a circulation system therefor, wherein fresh electrolytic solution entering the tank is directed more uniformly between the cathode and the anode plates.